title: Bond-strengthening in staphylococcal adhesion to hydrophilic and hydrophobic surfaces using atomic force microscopy.
abstract: Time-dependent bacterial adhesion forces of four strains of Staphylococcus epidermidis to hydrophobic and hydrophilic surfaces were investigated. Initial adhesion forces differed significantly between the two surfaces and hovered around -0.4 nN. No unambiguous effect of substratum surface hydrophobicity on initial adhesion forces for the four different S. epidermidis strains was observed. Over time, strengthening of the adhesion forces was virtually absent on hydrophobic dimethyldichlorosilane (DDS)-coated glass, although in a few cases multiple adhesion peaks developed in the retract curves. Bond-strengthening on hydrophilic glass occurred within 5-35 s to maximum adhesion forces of -1.9 +/- 0.7 nN and was concurrent with the development of multiple adhesion peaks upon retract. Poisson analysis of the multiple adhesion peaks allowed separation of contributions of hydrogen bonding from other nonspecific interaction forces and revealed a force contribution of -0.8 nN for hydrogen bonding and +0.3 nN for other nonspecific interaction forces. Time-dependent bacterial adhesion forces were comparable for all four staphylococcal strains. It is concluded that, on DDS-coated glass, the hydrophobic effect causes instantaneous adhesion, while strengthening of the bonds on hydrophilic glass is dominated by noninstantaneous hydrogen bond formation.
authors.affiliation: Department of Biomedical Engineering, University Medical Center Groningen and University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Niels P
authors.initials: NP
authors.lastname: Boks
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: Henny C
authors.initials: HC
authors.lastname: van der Mei
authors.forename: Willem
authors.initials: W
authors.lastname: Norde
mesh_terms: D020816:Amino Acid Motifs; D001422:Bacterial Adhesion; D005898:Glass; D006860:Hydrogen Bonding; D007477:Ions; D008024:Ligands; D008670:Metals / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods; D015233:Models, Statistical; D016012:Poisson Distribution; D011725:Pyridines / Q000737:chemistry; D013210:Staphylococcus / Q000378:metabolism*; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D007477:Ions; D008024:Ligands; D008670:Metals; D011725:Pyridines